Apparatus for post-tensioning and interconnecting re-enforcing wires using key hole anchor plates in a concrete structure



Feb. 18, 1969 G W I 3,427,772

APPARATU OR POST-TENSIO NING AND INTERCONNECTING RE-ENF'O NG WIRES USIKEY HOLE ANCHOR PLATES IN A CONC E STRUCTURE Filed Sept. 6, 1966 Sheetof 2 1N VENTOR.

ATTORNEY GEORGE W. WILLIAMS s. w. WILLIAMS 3, 7,7 2 APPARATUS FORPOST-TENSIONING AND INTERCONNECTING RE-ENFORCING WIRES USING KEY HOLEANCHOR PLATES IN A CONCRETE STRUCTURE Sheet Feb. 18, 1969 Filed Sept. e,1966 INVENTOR. GEORGE W. WILLIAMS ATTORNEY- (WM WCZ W Illl|++ llllllllIII United States Patent 2 Claims ABSTRACT OF THE DISCLOSURE Anapparatus and method for post-tensioning a concrete structure where thepost-tensioning wires extend in opposite directions and in substantialalignment with each other from a central recess in the structure andhave their outer ends anchored to the opposite sides of the structure.The inner wire ends have heads that can be inserted into keyhole slotsprovided in spaced apart inner anchor plates and then the wires can bemoved transversely into the narrow portions of the slots for causing theheads to bear against the inner plates. One or more washers may be usedon the wires to space the heads from adjacent plates to alter theeffective lengths of the wires. Tie Wires have heads at each end thatare receivable in the same slots that receive the wires and then the tiewires can be moved laterally into the narrow slot portions after theposttensioning wires have been tensioned and the tire wires with theinner anchor plates will constitute a connection between the alignedpost-tensioning wires that is substan'- tially in alignment with thesewires for post-tensioning the concrete structure.

An object of my invention is to provide an improvement over my twocopending applications, one on an apparatus and method forpost-tensioning aconcrete slab or the like, Ser. No. 554,081, filed May31, 1966; and the other on an apparatus and method for post-tensioningand interconnecting reenforcing wires in a concrete structure, Ser. No.559,996, filed June 23, 1966. In the earlier filed case the inner sidesof the cable wires were secured to two anchor plates that had'bayonetslots in their edges for receiving the wires. The wire ends had integralheads or beads and washers were placed next to the heads and pressedagainst the inner surfaces of the plates. The two-anchor plate wereforced toward each other for tensioning the wires that extended from theplates to opposite sides of the concrete structure. When the desiredtension was reached on the wires, tie wires or bolts were placed inother slots provided in the peripheries of the anchor plates and thesetie wires or bolts had washers bearing against the outer surfaces of theplates for holding the plates and maintaining the tensions on the wires.The use of slots in inner anchor plates permitted the wires to beconnected to the plates at the construction site. Shorter length wiresand cables could be used and this made their transportation to thebuilding site easier. Also shorter cables and wires can be handled andtensioned more readily than longer ones that extend between oppositesides of the concrete slab or structure. The interconnecting of theinner ends of the wires by the anchor plates and tie wires or bolts ineifect spliced the shorter length cables or wires together to makelonger ones that extended between opposite sides of the concrete slaband a uniform tension on both shorter cables was maintained by the tiewires or bolts.

In my other copending application, the inner ends of the shorter wiresand cables were connected to anchor plates that were moved away fromeach other for tensioning the cables rather than toward each other. Bothanchor plates had slots in their peripheries for receiving the wireends. The inner wire ends of one short cable overlapped the inner wireends of the other short cable and the length of the lapped wire endportions was the distance between the two spaced apart anchor plates.When the desired tension was reached on the wires and cables, shims wereplaced between the two anchor plates for holding them apart andmaintaining the same tension. Adjustable shims in the form of threadedrods with nuts and washers are also disclosed in the copending case.

An object of my present invention is to provide anchor plates that haveone or more key holes therein, the larger diameter portion of each keyhole being adapted to receive the head and one or more washers of one ormore cable wires so that these heads and washers can be passed throughthe key hole, after which the wire is moved into the narrow portion ofthe key hole for connecting the wire to the anchor plate. The tie wirecan have its head and one or more washers passed through the 'key holeafter which the tie wire is moved into the narrow key hole portion forconnecting the tie wire to the same anchor plate.

Where the anchor plates are moved toward each other for tensioning thewires and cables, the tie wires will extend between the two plates formaintaining the same tension on the cable wires. Anchor plates with keyholes in them for receiving cable and tie wires are stronger than thesame size and thickness of anchor plates with wirereceiving slots intheir peripheries because the key holes are entirely surrounded by metalwhile the periphery slots are open ended and thereby weakened. It isjust as easy to connect cable wires and tie wires to anchor plateshaving key holes for receiving them as it is to connect the cable andtie wires to anchor plates having slots in their edges.

The tension force is more directly in line between two cable wires thatare connected to two anchor plates by the use of key holes and where thetwo plates are also interconnected by a tie wire whose ends are receivedin the same key holes because the tie wire can lie adjacent to the twocable wires and be received in the same narrow portions of the key holesthat receive the cable wires. This permits thinner anchor plates to beused without the plates becoming bent under tension than is possible touse where the tie wires are received in separate slots from thosereceiving the cable wires in the anchor plates disclosed in my copendingapplications. Tie bolts can adjustably interconnect the two anchorplates and can be received in the enlarged portions of the key holesrather than in the narrow portions.

1 disclose a modified form of my invention wherein key holes are used inanchor plates that are moved away from each other for tensioning thecable wires rather than be moved toward each other.

Other objects and advantages will appear as the specification continuesand the novel features of the invention will be set forth in theappended claims.

Drawings For a better understanding of my invention, reference should bemade to the accompanying drawings, forming a part of this application,in which:

FIGURE 1 is a plan view of a concrete structure and shows my tensioningand re-enforcing apparatus in place.

FIGURE 2 is an enlarged transverse section taken along the line 22 ofFIGURE 1.

FIGURE 3 is a longitudinal section taken along the line 3-3 of FIGURE 2.

FIGURE 4 is a view similar to FIGURE 2, but shows the use of a tie boltand two cable wires arranged side by side and is taken along the line4-4 of FIGURE 5.

FIGURE 5 is a longitudinal section taken along the line 5-5 of themodified form shown in FIGURE 4.

FIGURE 6 is a plan view of a concrete structure and shows anothermodified form of my tensioning and reenforcing apparatus in place.

FIGURE 7 is an enlarged transverse section taken along the line 77 ofthe modified form shown in FIG- URE 6.

FIGURE 8 is a longitudinal section taken along the line 8-8 of FIGURE 7.

FIGURE 9 is a longitudinal section through a third modified form of myinvention.

While I have shown only the preferred forms of my invention, it shouldbe understood that various changes, or modifications, may be made withinthe scope of the annexed claims without departing from the spiritthereof.

Detailed description In carrying out my invention, I show in FIGURE 1 aconcrete structure indicated generally at A and having a central recessA1 and opposite outer parallel sides 1 and 2. It is possible to havemore than one recess A1 between the opposed sides 1 and 2 if desired. Anouter anchor plate B is placed against the side 1 of the concretestructure or slab A, and it may be partially embedded in the concrete ifdesired. A re-enforcing and post-tensioning cable C is attached to theouter anchor plate B, and it extends through the concrete from the side1 to the recess A1 in the concrete slab A. I have indicated the cable Cas being composed of two wires C in FIGURE 1, although in actualpractice the cable would be composed of any number of wires which couldbe combined to form a single cable with a single covering or could beindividual wires with individual coverings and an outer anchor plate foreach or a combination thereof, and I do not wish to be confined to anyexact number.

The portion of the cable C that is embedded in the concrete of the slabA may be sheathed in a plastic tube indicated generally at D and thelatter may be cut longitudinally and have overlapping edges defining thecut so that the cable may be readily inserted into the tube without thenecessity of threading the cable therethrough. The cable wires can alsobe independent of one another with each wire having its own covering.The scale of the drawing is small in FIGURE 1 and so I have indicatedthe cable C as extending through an opening in the outer anchor plate Band as being provided with only one beaded outer end 3 that bearsagainst a single washer 4 and the latter bears against the anchor plate.Each wire in the cable C will have its outer end provided with a head 3and a washer 4 and the anchor plate will have an opening for each cablewire. The cable comprising more than one wire or one or more wires incombination or separately could have a non-friction film applied to theportion that is to be embedded in the concrete so that this portioncould be tensioned with the rest of the cable during the tensioningoperation and would be free to move with respect to the concrete. Ifthis were done, the plastic tube or tubes D would not be needed.

Before describing how the inner ends of the wires from the cable C areconnected to an inner anchor plate E, it is best to state first thatanother cable F has its outer end secured to a second outer anchor plateG that in turn bears against the opposite side 2 of the concrete slab A,see FIGURE 1. The outer ends of the cable wires F extend throughopenings in the outer anchor plate G and are provided with beads orheads 5 and washers 6, the latter bearing against the anchor plate. Onlyone head 5 and one washer 6 are shown in FIGURE 1 because of thesmallness of the scale. The inner ends of the wires from the cable F areconnected to a second inner anchor plate H. The wires from the inner endof the cable C may be passed through a ring I or be independent of eachother and the wires from the inner end of the cable F may be passedthrough another ring K or be independent of each other. It is possibleto wrap tape or the like around the Wires of each cable rather than usea ring if it is so desired.

The purpose of the rings J and K or the wrapped tape is to prevent thecable wires from spreading apart too far. If each wire is independent ofthe others it would take its own position in the concrete slab and thenno ring or other device would be required. The cable F may be sheathedin a plastic tube D.

In FIGURES 2 and 3, I show on an enlarged scale how the wires from thecables C and F are connected to their respective anchor plates E and H.The anchor plate E is provided with one or more key holes 7. The largerdiameter portion of the key hole will permit the beaded inner end 8 ofone of the wires of the cable C and its associate washer 9 to be passedtherethrough and thenthe cable wire can be moved into the narrow portionof the key hole. The washer 9 will bear against the inner surface of theanchor plate. In like manner the inner anchor plate H is provided withone or more key holes 10 and the larger diameter portion of the key holewill permit the headed inner end 11 of one of the wires of the cable Fand its associate washer 12 to be passed therethrough after which thecable wire can be moved into the narrow portion of the key hole. Thewasher 12 will bear against the inner surface of the inner anchor plateH.

The key holes 7 and 10 are entirely enclosed by metal of the inneranchor plates and the plates are stronger because of this and may bemade thinner than the inner anchor plates shown in my copending caseswhere the cable wire receiving slots are in the edges of the plates andtherefore are open ended. Anchor plates provided with key holes canaccommodate more cable wires than the anchor plates having wirereceiving slots only in the edges of the plates. The key hole slots canbe so placed in the inner anchor plates as to provide space for thefingers of a hydraulic jack, not shown, to be applied to the plates formoving them toward each other for tensioning the cables C and F. I haveindicated by arrows 1313 the direction of force applied to the two inneranchor plates E and H when tensioning the cables C and F. Hydraulic ormechanical jacks may be used for this purpose.

It will be noted from FIGURE 1, that shorter cable lengths can be usedwhen post-tensioning a concrete structure A, where the cables do notneed to extend from the side 1 to the side 2. The tensioning of thecables can also be done at the center of the concrete slab A rather thanfrom either or both sides of the slab. Furthermore, the shorter lengthcables C and F need not be connected to the inner anchor plates E and Huntil at the construction site and the anchor plates need not beinterconnected by tie wires until after the shorter cables aretensioned.

In FIGURES 1, 2 and 3, I show tie wires L of predetermined lengths andbeing provided with an integral head at each end, indicated at 14 and15. A plurality of washers 16 are mounted on the tie wires L and one ormore may bear against the heads 14 or 15 to vary the effective length ofthe tie wire. The key hole 7 in the inner anchor plate E has itsenlarged portion capable of receiving the head 14 and one or morewashers 16 while the key hole 10 in the inner anchor plate H has itsenlarged portion capable of receiving the head 15 and one or morewashers 16. One or more tie wires L are moved into place in the keyholes 7 and 10 when the inner anchor plates E and H have been movedtoward each other to tension the shorter cables C and F to the desiredextent. The tie wire is moved into the narrow portions of the key holes7 and 10 and the washers 16 will contact with the outer surfaces of theinner anchor plates E and H to hold them in the position into which theyhave been moved by the hydraulic jacks, not shown, or the like.

The key holes 7 and 10 make it easy to assemble the cable wires C and Fand the tie wires L to the inner anchor plates E and H. Each key holecan accommodate one tie wire and one or more cable wires. The tie wiresL are dropped onto the cable wires as shown in FIGURE 3. Thus, when thecable wires have been stretched to the required amount, the tie wirescan be dropped in place, and when the tension is released on the anchorplates holding the cable wires, the load will be taken up by the tiewires which are immediately adjacent to the cable wires. Therefore theforce from the cable wires will be applied almost directly to the tiewire at practically the same point that the cable wire penetrates theanchor plate. The counteracting force of the tie wire is closer to thepoint where the initial force from the cable wires C and F is beingapplied. If additional 'tie wires are needed to balance the forceagainst the inner anchor plates, additional key hole slots can beprovided-in the plates for this purpose. The narrow portions of the keyslots 7 and 10 are long enough so that no part of the peripheries of thewashers overlies the larger diameter portions of the key holes. FIGURE 3clearly illustrates how the opposing washers 9 and 16 of the cable wireC and the tie wire L, overlap and therefore a portion of the force ofthe wire C against the anchor plate E is directly cancelled out to theextent that the washers 9 and 16 directly offset one another. The sameis true of the opposing washers 12 and 16 for the cable wire F and thetie wire L. This reduces the tendency of the anchor plates to bend andthinner anchor plates may be used.

In FIGURES 4 and 5, I show a slightly modified form of my invention. Theinner anchor plates M and N have key holes 25 and 26 with longer narrowportions that can receive two cable wires C and two cable wires F,rather than one as illustrated in FIGURE 3. The washers 9 on the cablewires C will abut one another and the Washers 12 on the cable wires Pwill abut one another. Instead of the tie wire L, I provide a bolt Pwhose diameter is slightly less than the larger diameter portions of thekey holes 25 and 26 and therefore these portions will receive the boltshank. The bolt head 27 and a washer 28 on the bolt bear against theouter surface of the inner anchor plate M while a nut 29 and a washer30, both mounted on the bolt, bear against the outer surface of theinner anchor plate N. If additional tie wires are needed to balance theforces against the inner anchor plates, additional key hole slots can beprovided in the plates for this purpose.

One or more bolts P may be used and they are under tension when the nuts29 are tightened to hold the inner anchor plates M and N in the positioninto which they have been moved by the post-tensioning means, not shown,for the shorter cables C and F. The diameter of the tie bolt P is largeenough to offset two cable wires C and F in FIGURE 5. Although the tiebolt is shown as being received in the enlarged portion of the key hole,it could be received in the narrow portion of the slot or in separatekey hole slots positioned in the anchor plates to balance the forcesagainst these plates.

FIGURES 6, 7 and 8, illustrate a further modified form of my invention.In this form the inner anchor plates Q and R are moved away from eachother when tensioning the cable wires C and F. The cable wire C has itsinner head 8 and washer 9 passed through the larger diameter portions ofkey holes 50 and 51 in the inner anchor plates Q and R, respectively.The wire is then moved into the narrow portions of the key holes asshown in FIGURES 7 and 8 and the washer 9 will bear against the outersurface of the anchor plate Q. The cable wire F has its inner head 11and washer 12 passed through the larger diameter portions of the keyholes 51 and 50 in the anchor plates R and Q, respectively and then thewire is moved into the narrow portions of the key holes, note the wire Fin FIGURE 7. The washer 12 will bear against the outer surface of theanchor plate R.

The inner anchor plates Q and R are forced apart by any means, notshown, and this force is indicated by the arrows 52 in FIGURE 6, andwill post-tension the cables C and F to the desired extent. Shims S areplaced between the anchor plates and will hold them in the position intowhich they have been moved so as to maintain the tension on the cables.The inner ends of the cable wires will overlap each other. It ispossible to make the narrow portions of the key holes 50 and 51, deeperso as to receive two cable wires in each narrow portion. This wouldpermit aligned slots in the two anchor plates R and Q in FIGURE 8, toeach receive one cable wire C and one cable wire F. The cable wire Cwould extend through both aligned key holes 50 and 51, as shown inFIGURE 8, and the other cable wire F, shown in FIG- URE 8, would alsoextend through the same two key holes 51 and 50 and be received in theirnarrow portions with the head 11 and washer 12 bearing against the outersurface of the anchor plate R. The concrete structure A, shown in FIGURE6 is the same as that shown in FIG- URE l and similar parts will begiven like reference letters and numerals and further description ofthis need not be given.

The modified form of the device shown in FIGURE 9 is like FIGURE 5,except that the tie rod T has threaded ends 7-5 and 76 and these arereceived in the enlarged portions of key holes 77 and 78 provided ininner anchor plates U and V. The narrow portions of the key holes arelong enough to receive two cable wires C that are superimposed one uponthe other. The inner ends of the cable wires have integral heads 8 andwashers 9 bear against the outer surface of the anchor plate V. Ifdesired it is possible to have aligned key holes 77 and 78 receive onecable wire C and one cable wire F that extends in an opposite directionfrom the wire C.

When the anchor plates are moved away from each other for tensioning thecable wires C and F, the nuts 79 and 80 may be rotated on the threadedends 75 and 76, respectively of the tie rod T so as to force the washers81 and 82, against the inner surfaces of the anchor plates U and V,respectively and hold them apart so as to maintain the tension on theshorter cables C and F. Further description of this form of the deviceneed not be given.

I have found that on small cables involving from one to four wires, itis more economical to cover the individual wires and allow each wire totake its position in the concrete slab rather than to combine thevarious wires into a single cable. On account of the tremendous forcesdeveloped during the tensioning of the cable wires, there is thepossibility of the unequal forces bending the single inner anchor platesunless the same can be equalized by changing the locations of the tiewires or tie bolts. One or more extra tie bolts or tie wires might needseparate key hole slots and these can be provided in the inner anchorplates and the operator can insert them in the desired slots to equalizethe pressures on the cable wires and plates.

The drawings do illustrate in FIGURES 1 and 6 a balancing of tensioningpressures on the cable wires and inner anchor plates with the wiresforming cables C and F. It is possible to have individual tensioningwires extend from the inner anchor plates and be arranged parallel toeach other as they extend to the outer anchor plates. In this event thewires would not form parts of cables to be tensioned. This is notillustrated in the drawings but comes within the spirit of my invention.

I claim:

1. A post-tensioning apparatus for a concrete structure comprising:

(a) a first cable having one end secured to a first outer anchor plate;

(b) a first inner anchor plate having key holes therein for receivingthe inner headed portions of the cable wires, the headed portions beingpassable through the enlarged diameter portions of the key holes and thewire portions being receivable in the narrow portions of the key holesso that the headed portions can bear against said plate;

(c) a second cable having one end secured to a second outer anchorplate;

(d) a second inner anchor plate spaced from said first posed adjacent toeach head and of a diameter that permits passage through the largerdiameter portion of the key holes in both of the inner anchor plates;

(c) whereby at least one washer on said inner wire ends may be disposedbetween the inner head of the wire and the adjacent inner anchor platefor altering the effective lengths of the wires, and at least one washeron said tie wires may be disposed between the heads at each tie wire endand the adjacent inner second cable wires will bear against said second10 plate; said second cable being substantially in line with andextending in the opposite direction from said first cable; and

(e) tie wires equal in number to the cable wires and anchor plate foraltering the effective lengths of said tie wires.

References Cited UNITED STATES PATENTS having h aded ends passablethrough the larger 6/1900 Hotz 52 223 tion of the same key 'holes insaid anchor plates 2340263 1/1944 Dodson 52 227 that receive the cablewires and having portions ad- 3225499 12/1965 Kourk.ene 52-130 jaeent tothe headed ends receivable in the narrow 3237357 3/1966 Hutchmgs 52 223ortions of the key holes in both anchor plates for 3285569 11/1966 La.Marr 254 29 interconnecting said plates so that each tie wire will1,796,913 3/1931 Wright 24 1231 b disposed adjacent to and substantiallyin align- 2,828,519 4/1958 Berg 24.1231 men: with the two opposing cablewires received in 2947118 8/1960 Rockwell 52*583 the same key holes thatreceive the tie wire. FOREIGN PATENTS 2. The combinatlon as set forth incla1m 1. and in 216,037 7/1961 Austria.

which 25 (a) the inner headed ends of each wire of the opposed cableshas a plurality of washers thereon of a diameter that permits them topass through the larger diameter portions of the key holes in both ofthe inner anchor plates; and

(b) each tie wire having a plurality of washers dis- ALFRED C. PERHAM,Primary Examiner.

JAMES L. RIDGILL, 111., Assistant Examiner.

US. Cl. X.R.

